Andaman Sea

The eastern Andaman Sea beyond Tenasserim combines continental shelves, steep slopes and deep troughs. Islands and submerged ridges divide the water into channels of different depth, while monsoon winds and strong tides reorganize currents, fishing grounds and sailing routes through the year. The northern shelf receives sediment from major mainland rivers and the mangrove coast of the Gulf of Martaban.

The Ayeyarwady and Salween carried immense loads of mud and sand toward the sea. Much sediment settled in the Gulf of Martaban as a thick mud wedge, while only a thinner layer spread across the narrow western Myanmar shelf. These deposits fed coastal fisheries and built shifting shoals that required careful local navigation.

Monsoon seasons set the rhythm of coastal trade and fishing. Sailors timed voyages between the southwest and northeast winds, and island communities used sheltered channels during storms. The sea lay beside an active tectonic boundary, where earthquakes in 1797 and 1833 showed the powerful movement beneath the seabed. Its working geography therefore joined distant river catchments, seasonal winds and a coast repeatedly reshaped by deposition and uplift.